I just did the Myer gift card thing again, but manually changed the category to Gift Cards and switched to the advanced listing tool, and it went through without the seller warning.

It may just be that I got the warning on my other ID as I have not sold a lot of things and still have a feedback below 10.

I would be interested to know if there is an 'unofficial' restriction seeing as eBay tried to steer me in to other categories on this ID which has a higher feedback total and many sold items, although not in recent times.